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2003 sl 500 launch edition
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33 Posts
Discussion Starter #1
i just bought a 2003 sl 500 for the wife. Car will be a weekend driver and it was suggested i get a trickle charger. i was looking at these 2:
CTEK Multi US 3300 12V Smart Battery Charger
by CTEK Power
$59.95
or
Battery Tender 021-0156 Battery Tender Plus 12V Battery Charger True Gel Cell Model
by Battery Tender
$47.48
prices are from amazon. i know the ctek is what mb uses for their branded models, but was wondering which might be better or any pros/cons???
from what i've read, i would need to hook it to the battery in the trunk and the jury is still out about leaving it on full time or turning it off/on.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,716 Posts
What you MIGHT need is battery maintainer. One that has floating circuit keeping the battery at about 13.5V.
There is lot of miss-advertisement on battery chargers, so do your homework before spending money on it. HF is selling battery maintainers for $5 on sale and they do work.
Now why would you need such an animal on the Mercedes? Do you park it for over a month at the time?
 

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1991 R129 500SL
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1,822 Posts
I personally went for the CTEK three years ago, and have not had any problems on my VARTA battery. I even went to ask help from a forum member, mertd93, to buy it and ship it to me.

IMHO, I wouldn't risk a cheap battery tender on my R129, more so on your R230, which has 2 batteries and a lot more electrical system, for a price difference of about US$40.

I hope this helps...
 

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E320/E250 Bluetec Ford F350 6.7l
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36,716 Posts
HF = harbor freight ???
saw this one for $9.99
Automatic Battery Float Charger - Battery - Automotive & Motorcycle
but it says Not for use on AGM batteries
That's the one. Have been using those on my RV, PWC, tractor and forklift for last 20 years.
Occasionally they fail like the more expensive models.
Do you have AGM batteries in your car? The main purpose of having those is not to worry about hooking up battery maintainer.
Looks like you have more homework to do. For long storage I found out that pulling the battery clamp off and recharging every 6 months is the best way. Than I bough expensive battery charger that does desulfating besides having float circuit.
 

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'03 CL500,& '07 GL450
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227 Posts
I've been using the Battery Tender Plus on my '03 CL500. The CL500 is stored during the winter here in Denver except for a monthly drive to check on all of the systems. The Tender has worked flawlessly. Never have had a problem in the electronics or the starting of the CL500.
 

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1993 MB 500E, 1965 MB 220b
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77 Posts
Battery Tender Jr. is among the best available & costs @$25 - 30. I've been using them successfully on my car & motorcycle batteries for years. You can attach the included "plug-in" harness to your battery clamps to make connect/disconnect a breeze. Perfect for any long or short-term storage situation.

These are the main features which sold me:
- for all lead-acid, flooded or sealed maintenance free batteries (AGM and gel cell).
- Microprocessor monitors voltage & automatically switches to float / maintenance voltage after fully charging the battery.
- If the battery voltage drops too far under load, full charger output power resumes.
- Solid state two color LED indicates stage of charger.
- Spark proof.
- Reverse polarity protected.
- compact size with 12' output cord.
- 5 year warranty
 

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C240, ML350 BlueTec
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36 Posts
The Harbor Freight maintainer does not provide the flexibility of the others - it will not saturate the charge on a low battery and is only intended to maintain a fully charged battery. I can't find enough information to tell if it only puts out 13.5 volts or if it has a brain. I suspect that there is no microprocessor to control the charging, and therefore nothing to protect the battery. I have used similar things before and they seem to shorten battery life. I certainly wouldn't keep it plugged in for weeks at a time.
The Battery Tender (BT) and CTEK units both provide all three to four stages necessary to take care of batteries in most all conditions, except bad batteries.
The BT website is very informative, if you are wondering about batteries or just want to learn about why the extra stages are important. Also check Battery Charging Tutorial | ChargingChargers.com
I have used BTs for many years now and I trust them completely. I am convinced that they prolong battery life, and I use five now.
I have just become aware of the CTEK units, and although their website is less informative than BT's, it looks like CTEK has one advantage over BT and that is the pulse technology designed to reduce sulphation. Any battery that has been discharged to 12.4 v will see some sulphation, so that technology might be useful to you. My full-size battery charger uses pulse, and it did save one battery that a conventional non-pulse charger couldn't bring back.
I need another "tender," so I think I'll choose one of the CTEK models or just get the accessory from my M-B dealer.
 

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C240, ML350 BlueTec
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Battery Trickle Charger

I just got a noco genius g1100 for my sl550. It works great! I leave it plugged in when we head up north. No risk of overcharging the battery. I am going to purchase another one for my harley. I like them better than the tender.
 
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